In a report issued on Wednesday, the World Food Programme (WFP) said that 60 percent of Yemenis, or 17 million people, were in “crisis” or “emergency” food situations.
"If humanitarian actors do not access all the people in need by the coming months, the situation may deteriorate dramatically," the report said.
The WFP warned that the provinces of Ta'izz and Hudaydah risked sinking into famine if they did not receive more aid.
It noted that the two Red Sea provinces "have the highest rates of global acute malnutrition in the country, ranging from 17 percent in Ta'izz city to 25 percent in Hudaydah."
According to the report, the other worst-affected Yemeni provinces are Lahij, Abyan, Sa’ada, Hajjah and Shabwah.
The Saudi military campaign has killed over 12,000 Yemenis since March 2015, according to a right NGO.
The Saudi war has also inflicted heavy damage on the impoverished country’s infrastructure.
Last month, the UN humanitarian chief warned that four countries were facing famine and starvation, and named Yemen as the most-affected one.
Stephen O'Brien said there were three million more chronically hungry people in Yemen than in January.